Muffler and method



June 16, 1964 BmGEL 3,137,365

MUFFLER AND METHOD Filed July 9, 1962 Z J J t J 20 ll 10 J9 J4 +17 17 United States Patent 3,137,365 MUFFLER AND METHOD Robert I. Binge], Arlington Heights, Ill., assignor to Mead Specialties Company, Inc., Chicago, IlL, a corporation of Illinois Filed July 9, 1962, Ser. No. 208,319

1 Claim. (Cl. 181-71) This invention relates to a mufller and method, and, more particularly, to a device for mufiling the sound of exhaust gas and a method for fabricating the device.

The instant invention finds utility in connection with pneumatic systems for the operation of power tools. In environments such as these, compressed air is delivered through suitable valving to an air cylinder, and, ordinarily, air must be exhausted simultaneously. The escaping exhaust air makes an unpleasant noise which may be uncomfortable to the artisans near the work area.

This problem has long been recognized and a variety of devices have been provided to serve as sound insulators. To a great extent, these either. employ carefully contrived and complex bafiles or some type of packing material. In any event, the prior art expedients have suffered from drawbacks, particularly the inability of the mufiling devices to stand up for prolonged periods.

It is a principal object of this invention to provide a novel muflling device and a method of fabricating the same which avoids the difliculties characteristic of the prior art.

Another object is to provide a mufiling device of sturdy construction and which is capable of withstanding the rigors of prolonged usage, the mufiling device including a cap-shaped element constructed of sintered bronze.

Still another object is to provide a muffiing device and method of fabrication in which the muffler portion is constructed of sintered bronze and is affixed, as by adhesive or molding, to a fitment employed as the terminus of an exhaust conduit for pressure fluid.

Yet another object is to provide a mufiler device in which the amount of escaping gas is selectively controlled.

Other objects and advantages of the invention, both general and specific, may be seen in the details of construction and operation set down in this specification.

The invention willbe explained in conjunction with an illustrative embodiment in the accompanying drawing in which--- FIG. 1 is an elevational view, partially in section, of a terminal fitting for an exhaust line equipped With a muffler embodying teachings of the invention; and

FIG. 2 is a sectional view such as would be seen along the sight line 2- -2 of FIG. 1. g

In the illustration given, the numeral designates generally a fitting such as may be constructed of brass and which is equipped with an elongated bore 11. Intermediate the ends 12 and 13 of the fitting 10, the outer surface of the fitting 10 is equipped with an annular shoulder portion 14, which, as can be seen from FIG. 2, is hexagonal in transverse section. The outer surface portion 15 of the fitting 10 is threaded so as to be received Within a coupling at the end of an exhaust line.

The outer surface 16 of the fitting 10 on the sideof hexagonal shoulder 14 opposite surface 15, is relatively smooth and is seen to carry a cup-shaped cap member 17. The cap member 17 isoptimally constructed of If the fitting 10 is constructed of bronze, the cap member 17 may be molded directly on the fitting 10.

In the illustration given, the cap 17 is apertured as.

at 18 in line with the bore 11. Threadedly received within the aperture 18 is a setscrew 19 suitably equipped with a jamb nut as at 20.

In the operation of the device, the fitting 10 is threaded into an exhaust line coupling (not shown), and the setscrew 19 is positioned in relation to the end 13 so as to release the amount of exhaust gas desired and thus control the speed of operation of an air cylinder, or the like.

Excellent results are obtained when the internal area of the cap 17 is several times the cross-sectional area of the bore 11, the exact ratio being best determined by the function of the application, i.e., the noise level. The internal area of the cap element 17 referred to is the effective area for release of gas such as compressed air, and may be in the range of l20 times the bore 11. On the M2" NPT muffler, the ratio was 9, and on the /2 NPT, it was 2 /2.

The following specific example shows details of a preferred construction:

0 Example The sintered element 17 is made from A.M.D. No. 46 bronze filterpowder and is composed of about 94% copper and 6% tin, the finished product having a density of 4-5 grams per cc. I

The particle size of the powder is controlled'by having 99% pass through a No. 40 mesh screen and 99% retained by a No. 60 mesh screen. Some alteration of the particle size maybe desired to change the mufiling and air flow characteristics.

The powder isintroduced into a mold conforming to the outer shape of the cap 17. Normally, the mold will be contoured so as to provide a closedend for the cap as at 17a in FIG. 1. Thereafter, an epoxy adhesive is employed to unite the sintered bronze cap member 17 to the brass fitting 10. Brass is preferred because of its more economical price. The epoxy adhesive was Bondmaster M-688, fortified with Hardener C-H8 provided by Rubber &'Asbestos Corp. I

Where bronze is used as the material of construction of fitting 10, I have found that the molding operation results in a tight fit between the sintered bronze cap 17 and the fitting 10 in the area of the surface 16. This 'may be further strengthened, if desired, through the use of an adhesive or by undercutting the surface 16, i.e., notching, etc., so as to provide a keying action.

The sintered bronze cap resulting from this operation is relatively frangible, having a tensile strength of the order of 5000-7000 p.s.i. Howeventhe cap 17 may be suitably tapped to provide the threaded aperture 18 for the receipt of the setscrew 19.

I have also found that tolerances are more easily maintained if both the surface 16 andthe outer surface 17b of the cap 17 are slightly outwardly tapered so as to develop a frusto-conical configuration.

While, in the foregoing specification, I have set down a detailed description of an embodiment of the invention for the purpose of explanation thereof, many variations in the details herein given may he made by those skilled in the art without departing from the spirit and scope of the invention.

I claim:

A device for mulfiing exhaust gas, comprising an e1ongated tubular flow fitting having a bore extending longitudinally therethrough, an annular shoulder extending transversely outwardly of said fitting intermediate the ends thereof, said fitting on one side of said shoulder being equipped with threads for coupling said fitting to an exhaust line, and a sintered bronze cap secured to the outer surface of said fitting on the other side of said shoulder, said cap having a threaded aperture aligned with said bore, a setscrew mounted in said aperture, and a jamb nut on said sets'crew external to said cap, said setscrew being mounted for positioning adjacent the end of said bore to control the flow of exhaust gas through said device, said 7 cap having an internal area of from about two and onehalf to nine times the cross-sectional area of said bore.

References Cited in the file of this patent UNITED STATES PATENTS 1,113,410 Coifill Oct. 13, 1914 1,567,298 Reinhardt Dec. 29, 1925 2,576,610 Kunzog Nov. 27, 1951 2,950,775 Zwayer Aug. 30, 1960 FOREIGN PATENTS 511,919 Germany Nov. 4, 1930 

